This is kinda cool. One of my biggest frustrations in dealing with a development team that doesn’t sit in the same place as you do because showing them what you mean with a drawing is almost impossible. I suppose you could mock-up stuff in Excel, but, really, you might as well stab yourself with a fork. Or you could draw something on paper, scan it and email it around, but what if you don’t have access to a scanner or want to change something? Or, you could go through your User Experience group, but that’s a big gun for what might be a small problem.
Balsamiq allows you to create mockups pretty quickly – not as quickly as scribbling something on paper, but pretty close. It seems like a good tool for Product Managers in a high iteration process.